What do the Gram stain, the acid-fast stain; and the endospore stain have in common? Select one: They are used on a wet mount of the specimen They use heat to force the dye into cell structures. The staining outcome varies with the charge of the cell wall: They use a negative stain technique. They are differential stains
The Correct Answer and Explanation is:
The correct answer is: They are differential stains.
Explanation:
Differential stains are used to distinguish between different types of microorganisms or different cell structures based on their staining properties. The Gram stain, acid-fast stain, and endospore stain are all examples of differential stains because they each target specific components of the cell structure, resulting in different staining outcomes that help identify the microorganism or its features.
- Gram Stain:
The Gram stain is used to differentiate bacteria based on the composition of their cell walls. Bacteria with thick peptidoglycan layers (Gram-positive bacteria) retain the crystal violet dye and appear purple under the microscope, while those with thinner peptidoglycan layers (Gram-negative bacteria) do not retain the dye and appear pink after a counterstain (usually safranin). This differential staining method helps identify bacterial species and informs treatment decisions, such as choosing antibiotics. - Acid-Fast Stain:
The acid-fast stain is primarily used for identifying Mycobacterium species, such as Mycobacterium tuberculosis, the causative agent of tuberculosis. These bacteria have a waxy, lipid-rich cell wall that does not easily absorb common stains. The acid-fast stain uses heat and phenol to force the dye (usually carbolfuchsin) into the cell wall. Acid-fast bacteria retain the red dye even after washing with acid alcohol, while non-acid-fast bacteria do not, appearing blue with the counterstain methylene blue. - Endospore Stain:
The endospore stain targets bacterial endospores, which are highly resistant structures formed by some bacteria (like Bacillus and Clostridium) under adverse conditions. The endospore stain uses heat to drive malachite green dye into the spores, which retain the green color, while the vegetative cells take up a red counterstain (usually safranin).
In all three cases, these stains involve using heat or other techniques to differentiate cells or cell structures based on their ability to retain specific dyes. These methods are fundamental in microbiology for bacterial identification and understanding microbial properties.
